The present invention relates to pneumatic cleaning systems. More specifically, the present invention relates to pneumatic belt hole cleaning systems for vacuum transport systems.
Direct-to-media printing systems typically include a printable media hold-down system. As a printable medium passes on a transport surface under a print head, the hold-down system attempts to maintain a critical print head to printable media gap as well as to prevent contact between the printable medium and the print head. Contact between printable media and the print head may result in contamination of the printable media as well as fibers from printable media becoming lodged in ink nozzles in the print head. Over time, a substantial number of fibers could become lodged in the nozzles causing the print head to clog. A clogged print head can damage printable media by printing incorrectly, waste ink, and cause significant downtime as the clogged head must be cleaned and/or replaced.
Several hold-down systems are prevalent in modern direct-to-media printing systems. One example is a vacuum/chamber transport system. In this system, a series of small holes are placed in the transport element surface, and air is sucked through the holes, away from the print head (or print head array). As the printable medium passes under the print head (or print head array), a vacuum is created under the printable medium, thereby holding the printable medium against the transport surface.
FIG. 1 illustrates an exemplary vacuum transport system 100. A printable medium 102 is transported past a print head array 104 on a transport belt 106. The transport belt 106 may be made of a highly porous material or a nonporous material with a number of holes for allowing air flow through the transport belt. These holes may be small in size (e.g., 1.0 mm in diameter) and spaced evenly apart on the transport belt 106. A vacuum blower 108 creates a vacuum pressure that is directed through a vacuum chamber 110 to the transport belt 106. The vacuum pressure pulls air through the transport belt 106 toward the vacuum blower 108 (as indicated by arrow A). The vacuum chamber 110 acts as a diffuser, spreading the vacuum pressure equally over the surface of the transport belt 106. As the printable medium 102 advances, the vacuum pressure pulls the printable medium against the transport belt 106, thereby protecting the print head array 104 from contact with the printable medium as well as providing a necessary tacking force to transport the printable medium with the transport belt through a print zone.
Vacuum hold-down systems have inherent problems, however. One problem is clogged holes in the transport belt. Fibers from the printable media, dust and debris from the ink such as stray ink drops may become lodged in the individual holes in the transport belt, thereby reducing or completely blocking the flow of air through that hole. Over time, enough holes may become clogged in the transport belt to reduce the overall vacuum pressure created by the vacuum hold-down system to a level where a printable medium may contact an individual print head (or multiple print heads in a print head array). Additionally, when a hole is clogged, dirt may be transferred to the side of the printable medium touching the vacuum belt resulting in imperfections on the printable medium.
One approach to eliminate this problem is to periodically remove the transport belt from the system in which it is installed and clean the holes in the transport belt. However, this approach results in significant downtime for the print system, as printing must be halted in order to remove the belt.